Ultrasonic Diagnosis of Ischemic Cardiodisease
A diagnostic imaging method and ultrasound system are described for detecting abnormalities of the left ventricle of the heart. A sequence of images including the mitral valve is acquired and processed to identify the location of the mitral valve in each of the images in the sequence. A graphic is displayed with the images depicting the location of the mitral valve in the current image and in each of the preceding images of the sequence. Preferably the mitral valve location is identified by automatic detection of the mitral valve plane in each of the images. A desirable graphic color-codes each of the successively different mitral valve locations in the graphic. The image and graphic can be viewed in real time to discern the effects of conduction delay and infarction of the left ventricle.
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This invention relates to ultrasonic diagnostic imaging systems and, in particular, to ultrasonic imaging diagnosis of ischemic cardiac disorders.
The present invention relates to an ultrasonic diagnosis apparatus and method in which movement of an organ in motion, such as the cardiac muscle (myocardium) of a heart, is obtained and displayed and if necessary, on the basis of the movement, diagnosis of ischemic and other functional disorders is performed. In particular, the ultrasonic diagnostic apparatus and method relate to an apparatus and method effective in diagnosis of ischemic cardiac diseases such as myocardial ischemia and angina pectoris, left ventricular distention disorders including hypertrophic cardiomyopathy, and disorders of the conducting system of the heart such as Wolff-Parkinson-White syndrome and left bundle branch block.
In diagnosis of the above-mentioned ischemic cardiac diseases, left ventricular distention disorders and disorders of the conducting system of the heart are of considerable interest. But with conventional B mode imaging it is very difficult to acquire detailed information with respect to detection of local deteriorated portions in contraction ability in ischemic cardiodisease, objective diagnosis of left ventricle distention disorders, and detection of the positions and extent of abnormal paries movement in a conducting system of the heart.
One approach to overcoming this difficulty is an analytical method of paries movement of the left ventricle. This method measures changes in thickness of the cardiac muscle of the left ventricle at both systole and diastole and concludes that a region of lesser change in thickness is a region of reduced contraction ability or ischemic region. There have been various algorithms proposed for this method which generally require tracing the endocardium or the epicardium of the left ventricle in both end-systole and end-diastole views on B-mode tomographic images.
Stress echography is also known for diagnosing myocardial ischemia. Carrying out a stress echography procedure requires a heart to be stressed by exercise, drugs or an electric stimulus. B mode tomographic images of the heart are recorded before and after stressing, respectively, and displayed side-by-side in comparison. Changes in thickness of the cardiac muscle are compared in systolic and diastolic views (normally, thicker in systole) to detect a region of myocardial infarction. It is also generally required for this detection to trace the inner and outer walls and the center line of the cardiac muscle on the images to define the contour of the myocardium.
A number of automated and semi-automated techniques have been developed for defining the myocardium by tracing its boundaries in an ultrasound image. For example, U.S. Pat. No. 6,491,636 (Chenal et al.) describes a technique for automatically tracing the endocardial border of the left ventricle of the heart which uses corner templates and septal wall angle bisection to geometrically identify the medial mitral annulus, the lateral mitral annulus and the apex of the left ventricle, then fits a border template to the three identified landmarks in the image. U.S. Pat. No. 6,346,124 (Geiser et al.) traces both the endocardial border and the epicardial border by image analysis using expert reference echocardiographic image borders. See also U.S. Pat. No. 5,797,396 (Geiser et al.) which describes a technique for identifying elliptical borders in ultrasound images. Another automated border tracing technique is described in U.S. patent application Ser. No. 60/526,574. In this technique a user begins by delineating first and second landmarks on a tissue boundary of a diagnostic image such as the medial and lateral mitral annuli of the left ventricular endocardium. The user then delineates a third landmark on the tissue boundary such as the ventricular apex and a processor then fits a border template to this first tissue boundary, the endocardium. The user delineates a fourth landmark on another boundary of the tissue such as the epicardium and the processor fits a second border template to the second tissue boundary. The template shapes can then be adjusted by the user to precisely match the epicardial and endocardial boundaries.
The robustness of the tracing technique is ultimately determined by the quality of the image, however. Cardiac imaging can pose a number of challenges to image quality. The heart is enclosed in the rib cage which limits the acoustic windows available for cardiac imaging. The heart is often scanned from below the ribs with the heart viewed from the apex, requiring the ultrasound to penetrate through and return from a considerable distance into the body. Such apical views cause the beam directions to be almost parallel to the lateral wall of the left ventricle rather than orthogonal which would return the strongest echoes. The endocardial lining is a delicate tissue which often is not a strong reflector of ultrasound energy. And of course, the heart is in constant motion. Consequently, the endocardial border cannot always be traced with utmost confidence. Accordingly it is desirable to provide diagnostic techniques for ischemic and arterial cardiodiseases which can assess left ventricular infirmities without the need to continually define the endocardial border.
In accordance with the principles of the present invention, an ultrasonic diagnostic apparatus and technique are provided for diagnosing ischemic cardiac disorders. The mitral valve location is distinguished in a sequence of real time images of the left ventricle as it moves with expansion and contraction of the heart chamber. The valve location over at least a portion of the heart cycle is retained in the images such that the buildup of a sequence of successive valve locations is displayed. The variation in the changes in valve location reveal defects in conduction and motion of the heart wall. In accordance with a further aspect of the present invention the mitral valve location is distinguished by a representation of the mitral valve plane in a cross-sectional view of the valve.
In the Drawings
Physicians commonly must diagnose patients exhibiting symptoms of heart failure, constriction or restriction. Observing and measuring the motion of the heart muscle with ultrasound is routinely done by cardiologists in these situations. In conventional practice physicians examine both the systolic contraction and diastolic relaxation with spectral Doppler to analyze motion of the mitral annulus, the ring of leaflet attachment in the left ventricle (LV). This analysis can be used to estimate the timing and overall motion of the LV during contraction as well as understanding the nature of constrictive and restrictive diseases of the myocardium. For example, late contraction of the LV lateral wall results in delayed excursion of the mitral annulus on that side. The present invention describes apparatus and a method for detecting and quantifying these motional aberrations of a diseased heart. This invention describes the tracking of mitral annular motion for parametric display of mitral annular motion; use of this tracking information to map Doppler motion onto the parametric display; and to quantify both the timing and degree of excursion of mitral annular motion.
Referring now to
The ultrasound system of
In accordance with the principles of the present invention the location of the mitral valve is tracked and depicted on the ultrasound image during the systolic phase, the diastolic phase, or both. A sequence of images acquired during a heart cycle are analyzed to detect the mitral valve annulus as described below or by other known techniques. Preferably the position of the mitral annulus is detected rather than the valve leaflets to provide a more stable motional reference. The mitral valve location is graphically marked on an image as by a distinctive line or color stripe. This process is repeated for the next and all successive images in the sequence. Furthermore, the lines or stripes are accumulated so that each new image retains the lines or stripes identified in the previous images in the sequence and in the same locations in relation to a static reference in which they were detected. As the sequence progresses the lines or stripes build up, depicting the path of successive positions of the mitral valve during the sequence of contraction or expansion. A build-up 5 of such color stripes is shown in
Each time the predetermined heart phase or phases have completed and the mitral valve motion 5 depicted for that heart cycle interval has been fully depicted, the build-up of lines or stripes is deleted until the predetermined phase starts again during a successive heart cycle. If the user decides to depict the mitral valve motion during systole the first line or stripe will be drawn at a lower position on the display and continually move upward as the heart contracts and the mitral valve moves toward the apex of the heart. If the user decides to depict mitral valve motion during diastole the lines or stripes will begin at a higher position on the display and progressively build up toward the bottom of the screen as the heart muscle relaxes and the mitral valve location moves away from the apex. If both heart phases are chosen the build-up of colors or shades will alternately move upward and then downward on the screen.
One technique for detecting the location of the mitral valve in a sequence of heart images is shown starting with
A filter template defining the anticipated shape of the MMA is then cross-correlated to the pixels in the MMA search area. While this template may be created from expert knowledge of the appearance of the MMA in other four-chamber images as used by Wilson et al. in their paper “Automated analysis of echocardiographic apical 4-chamber images,” Proc. of SPIE, August, 2000, the illustrated example uses a geometric corner template. While a right-angle corner template may be employed, in a constructed embodiment an octagon corner template 28 (the lower left corner of an octagon) is used as the search template for the MMA, as shown at the right side of
Once the MMA has been located a similar search is made for the location of the LMA, as shown in
With the MMA 26 and the LMA 36 found as shown in
This technique for identifying the mitral valve plane may be continued to define the full endocardial border as follows. While this continuation is not necessary in an implementation of the present invention, and may in fact be undesired for the additional graphical complexity it introduces into the images, it may be desired for further diagnostic purposes such as producing a color representation of LV wall motion known as color kinesis and described in U.S. Pat. No. 5,533,510 (Koch, III et al.)
To trace the full endocardial border an additional landmark, the endocardial apex, is found. The position of the endocardial apex may be determined as shown in
Once these three major landmarks of the LV have been located, one of a number of predetermined standard shapes for the LV is fitted to the three landmarks and the endocardial wall. Three such standard shapes are shown in
The chosen shape is then fitted to the border to be traced by “stretching” the shape, in this example, to the endocardial wall. The stretching is done by analyzing 48 lines of pixels evenly spaced around the border and approximately normal to heart wall. The pixels along each of the 48 lines are analyzed as shown in
With the end systole border drawn in this manner the ABD processor 490 now proceeds to determine the end diastole border when the end diastole image is in the sequence. It does so, not by repeating this operation on the end diastole image 16, but by finding a border on each intervening image in sequence between end systole and end diastole (or vice versa). In a given image sequence this may comprise 20-30 image frames. Since this is the reverse of the sequence in which the images were acquired, there will only be incremental changes in the endocardial border location from one image to the next. It is therefore to be expected that there will be a relatively high correlation between successive images. Hence, the end systole border is used as the starting location to find the border for the previous image, the border thus found for the previous image is used as the starting location to find the border for the next previous image, and so forth. In a constructed embodiment this is done by saving a small portion of the end systole image around the MMA and the LMA and using this image portion as a template to correlate and match with the immediately previous image to find the MMA and the LMA locations in the immediately previous image. The apex is located as before, by bisecting the angle between the upper portions of the septum and lateral LV wall, then locating the endocardium by the maximum slope of the brightness gradient. Since the LV is expanding when proceeding from systole to diastole, confidence measures include the displacement of the landmark points in an outward direction from frame to frame. When the three landmark points are found in a frame, the appropriately scaled standard shape is fit to the three points. Another confidence measure is distention of the standard shapes; if a drawn LV border departs too far from a standard shape, the process is aborted.
Border delineation continues in this manner until the end diastole image is processed and its endocardial border defined. The dual display then appears as shown in
As
Further details of this endocardial border technique may be found in U.S. Pat. No. 6,491,636 (Chenal et al.)
A second embodiment for identifying the location of the mitral valve is illustrated in
In accordance with the principles of another embodiment of the present invention, the mitral valve plane of the left ventricle is delineated by an assisted border detection technique as follows. The user displays an image 92 on which the mitral valve plane is to be located as shown in
As in the previous embodiment, the process used to define the mitral valve plane can be continued to trace the full endocardial border. After identifying the MMA and LMA control points in the image 92, the user then moves the pointer to the endocardial apex, which is the uppermost point within the left ventricular cavity. As the user moves the pointer to this third landmark in the image, a template shape of the left ventricular endocardial cavity dynamically follows the cursor, distorting and stretching as the pointer seeks the apex of the chamber. This template, shown as a white line in
With the endocardial border thus defined, the user can continue to define the epicardial border. The user moves the cursor to the epicardial apex, the uppermost point on the outer surface of the myocardium. The user then clicks on the epicardial apex and a fourth control point marked “4” is positioned. A second template then automatically appears which approximately delineates the epicardial border as shown in
A diseased heart may be afflicted by a conduction delay on one side of the heart relative to another. When the heart contracts the myocardium should conduct the contractive motion instantaneously throughout the heart muscle. An abnormal heart may exhibit a delay in this contractive motion in a particular region of the heart.
If the patient has suffered a myocardial infarction (heart attack) one side of the mitral valve plane can appear to hardly move at all. Such a condition is illustrated by
It is thus seen that the technique of the present invention can detect abnormal heart conditions even when the endocardial border is indistinct and too faint to be accurately traced. For instance, the white arrow in the end diastole image on the left side of
The technique of the present invention may be extended to three dimensional imaging. In 3D imaging the entire mitral valve location can be visualized, not just a cross-section as shown in the preceding examples. Depending on the graphical object in which it is decided to represent the valve plane location, the motional graphic may appear as a growing cylinder, cube, or other shape, and may be shaded or color-coded as described above. In a healthy heart the object will grow uniformly in shape but in a diseased heart the shape may appear nonuniform with a sloped or slanted surface or coloring. The tissue of the heart can be made semi-transparent so as to better visualize the mitral valve location graphic within the 3D image of the heart. Shading the graphic can cause the graphic to appear more distinct within the anatomy.
It will also be apparent to those skilled in the art that quantified numerical measures or representations of the excursions of the mitral valve annulus can be derived from the color coding or spacing of the successive mitral valve location lines or surfaces. Both valve positions and rates of change in position (derivatives of positional change or velocity) can be displayed to assist in the diagnosis. By restricting the motional graphic to the mitral valve location rather than the full endocardial border as is done in color kinesis, the clinician is provided with a relatively uncluttered image sequence from which to make a diagnosis.
Claims
1. A method for depicting the functioning of the heart from a sequence of images acquired during a phase of the heart cycle comprising:
- acquiring a sequence of images of the heart during a selected phase or phases of the heart cycle, which images include the mitral valve;
- segmenting and distinctively distinguishing from the rest of each image the location of the mitral valve in the images of the sequence; and
- displaying in a single heart image the progressive locations of successive positions of the mitral valve during a real time display of the sequence of images.
2. The method of claim 1, wherein displaying further comprises displaying in a single heart image the distinctively differently displayed locations of successive positions of the mitral valve.
3. The method of claim 2, wherein identifying further comprises identifying the location of the mitral valve annulus in the images; and
- wherein displaying further comprises displaying in a single heart image the locations of successive positions of the mitral valve annulus.
4. The method of claim 3, wherein identifying comprises identifying the location of the mitral valve annulus as shown in cross-section in a sequence of two dimensional images.
5. The method of claim 3, wherein identifying comprises identifying the location of the mitral valve annulus as shown in a sequence of three dimensional images.
6. The method of claim 2, wherein identifying further comprises identifying the location of the mitral valve plane in the images; and
- wherein displaying further comprises displaying in a single heart image the locations of successive positions of the mitral valve plane.
7. The method of claim 6, wherein identifying comprises identifying the location of the mitral valve plane as shown in cross-section in a sequence of two dimensional images.
8. The method of claim 6, wherein identifying comprises identifying the location of the mitral valve plane as shown in a sequence of three dimensional images.
9. The method of claim 2, wherein displaying further comprises displaying in a single heart image the distinctively differently shaded locations of successive positions of the mitral valve.
10. The method of claim 2, wherein displaying further comprises displaying in a single heart image the distinctively differently colored locations of successive positions of the mitral valve.
11. The method of claim 1, wherein displaying further comprises displaying in each of a plurality of images of the sequence the location of the mitral valve in that image and the location of the mitral valve in previous images in the sequence.
12. The method of claim 11, further comprising resetting the display of a plurality of locations of the mitral valve following the end of the selected phase or phases of the heart cycle; and
- repeating the acquiring, identifying and displaying steps during another heart cycle.
13. The method of claim 1, wherein identifying further comprises manually identifying at least one reference point of the mitral valve in an acquired heart image.
14. The method of claim 1, wherein identifying further comprises identifying the location of the mitral valve by automated border detection processing of the images.
15. An ultrasonic diagnostic imaging system for analyzing the performance of the heart comprising:
- a probe having a plurality of transducer elements;
- an image processor coupled to the probe which acts to produce a sequence of B mode images;
- an automated border detection processor, which operates to identify the location of the mitral valve in a sequence of B mode images;
- a graphic display processor, responsive to the identification of the location of the mitral valve in a sequence of B mode images, which act to produce a graphic distinctively depicting the locations of the mitral valve from the rest of the image in a sequence of real time B mode images; and
- a display responsive to the graphic display processor which acts to display a sequence of B mode images with a graphic depicting the progressive locations of the mitral valve in previous images in the sequence.
16. The ultrasonic diagnostic imaging system of claim 15, further comprising a Cineloop memory, coupled to the automated border detection processor, which stores a sequence of B mode images.
17. The ultrasonic diagnostic imaging system of claim 15, wherein the graphic display processor further comprises a processor which acts to produce a graphic depicting the locations of the mitral valve in a sequence of B mode images by distinctive colors.
18. The ultrasonic diagnostic imaging system of claim 15, wherein the automated border detection processor further comprises a processor which operates to identify the location of the mitral valve plane in a sequence of B mode images.
19. An ultrasonic diagnostic imaging system for analyzing the performance of the heart comprising:
- a probe having a plurality of transducer elements;
- an image processor coupled to the probe which acts to produce a sequence of B mode images;
- a user control by which a user can identify the location of the mitral valve in at least one of a sequence of B mode images;
- a graphic display processor, responsive to the identification of the location of the mitral valve in a sequence of B mode images, which act to produce a graphic distinctively depicting the locations of the mitral valve from the rest of the image in a sequence of B mode images; and
- a display responsive to the graphic display processor which acts to display a real time sequence of B mode images with a graphic depicting the progressive locations of the mitral valve in previous images of the sequence.
20. The ultrasonic diagnostic imaging system of claim 19, further comprising a border detection processor, responsive to the user control, which acts to identify the mitral valve location in a sequence of B mode images.
21. The method of claim 1, wherein displaying further comprises displaying in a single heart image the locations of successive positions of the mitral valve during the sequence of images in the absence of the display of successive positions of at least a portion of the endocardial wall, whereby image clutter is reduced.
Type: Application
Filed: Jul 19, 2005
Publication Date: Apr 24, 2008
Applicant: KONINKLIJKE PHILIPS ELECTRONICS N.V. (EINDHOVEN)
Inventors: Ivan Salgo (Andover, MA), Andrew Davenport (Dracut, MA), William Kelton (Manchester, NH)
Application Number: 11/573,214
International Classification: A61B 8/13 (20060101);